An electric vehicle is required to have long drive distance per charging. For example, a battery of a plug-in type electric vehicle is charged by commercial power utility (100V) before a drive. The electric vehicle is required to have longer drive distance without additional charging when the drive is started with the fully charged state.
JP-A-2010-12970 describes an electric vehicle having an engine air-conditioning mode and a battery air-conditioning mode. In the engine air-conditioning mode, air-conditioning is performed using output of a relatively small engine. In the battery air-conditioning mode, air-conditioning is performed using electric power of a battery.
In the engine air-conditioning mode, a cooling operation is conducted by driving a refrigerant compressor of a refrigerating cycle using a rotation torque of an output shaft of the engine, and a heating operation is conducted using exhaust heat of the engine. In the battery air-conditioning mode, a cooling operation is conducted by driving the refrigerant compressor with the electric power of the battery, and a heating operation is conducted using an electric heater.
The electric vehicle is required to use the electric power charged in the battery prior to using fuel for the engine. In JP-A-2010-12970, the engine is activated when a remaining power of the battery becomes equal to or lower than a predetermined value. At this time, the battery air-conditioning mode is switched to the engine air-conditioning mode. The drive distance per charging is increased in such manner.
The timing for activating the engine is set based on the remaining power of the battery. However, if a load of a cooling operation is small, it may be better to make the timing for activating the engine late. For example, when a preset temperature is relatively high or when a temperature of outside air is relatively low, the load of the cooling operation is determined as small. In contrast, if the load of the cooling operation is high, it may be better to make the timing for activating the engine early so as to increase the drive distance.
Also in the heating operation, the suitable timing for activating the engine may be different based on not only the remaining power of the battery but also a load of the heating operation.